setting __hash__ method to parent class implementation
adding `get_POAV_attr` method to `POAV` classes and renaming bond attrs
adding `get_POAV_attrs and POAV1/POAV2/POAVR property methods
Adding custom container classes for sequences of
`Point`s and `Vector`s.
changing starting index for iterating over unit cell points from 1 to 0
adding `--debug` command-line option
adding `debug` kwarg to StructureBase constructor
Fix unit cell method math.

Adding a check to fix case where on the first loop, one atom may
end up outside the unit cell in the negative z axis.

Also adding debug option output of coordinates.